[base] Move many files into base

Moved from include/private into include/private/base:
 - SkAlignedStorage.h
 - SkContainers.h
 - SkFloatBits.h
 - SkPathEnums.h
 - SkTArray.h
 - SkTDArray.h
 - SkTypeTraits.h
 - SkVx.h
 - SkCPUTypes.h*

Moved from include/core into include/private/base:
 - SkMath.h
 - SkSpan.h

We still want SkSpan.h to be a part of the public API,
so include/core/SkSpan.h still exists, it just includes
include/private/base/SkSpan_impl.h

We want to remove SkMath.h from the public API (most
client uses have been removed already), but for now
it too has a shim header file in include/core/SkMath.h

As per the design of base, there are no includes inside
of base on Skia files not also in base. SkLeftShift moved
out of SkTypes.h and into SkMath.h, as that seemed like a better
fit. U8CPU and U16CPU moved into their own file, SkCPUTypes.h
while we decide where their future lies.

Suggested review order:
 - include/private/base/BUILD.bazel
 - include/private/BUILD.bazel
 - include/BUILD.bazel
 - gn/*.gni (these are generated from the BUILD.bazel files)
 - BUILD.gn
 - public.bzl
 - Everything else, mostly done with find and replace and
   cleaned up with the rewrite_includes.py script.

Change-Id: Icce0d0c445863c6908b63ec31b9595de400988dc
Bug: skia:13983
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/629317
Reviewed-by: Ben Wagner <[email protected]>
Commit-Queue: Kevin Lubick <[email protected]>
Owners-Override: Kevin Lubick <[email protected]>
diff --git a/tests/GrMemoryPoolTest.cpp b/tests/GrMemoryPoolTest.cpp
index 4c7f35a..1390fb4 100644
--- a/tests/GrMemoryPoolTest.cpp
+++ b/tests/GrMemoryPoolTest.cpp
@@ -5,8 +5,8 @@
  * found in the LICENSE file.
  */
 
-#include "include/private/SkTArray.h"
-#include "include/private/SkTDArray.h"
+#include "include/private/base/SkTArray.h"
+#include "include/private/base/SkTDArray.h"
 #include "include/utils/SkRandom.h"
 #include "src/gpu/ganesh/GrMemoryPool.h"
 #include "tests/Test.h"